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//===-- Support/DJB.cpp ---DJB Hash -----------------------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains support for the DJ Bernstein hash function.
//
//===----------------------------------------------------------------------===//
#include "llvm/Support/DJB.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/ConvertUTF.h"
#include "llvm/Support/Unicode.h"
using namespace llvm;
static UTF32 chopOneUTF32(StringRef &Buffer) {
UTF32 C;
const UTF8 *const Begin8Const =
reinterpret_cast<const UTF8 *>(Buffer.begin());
const UTF8 *Begin8 = Begin8Const;
UTF32 *Begin32 = &C;
// In lenient mode we will always end up with a "reasonable" value in C for
// non-empty input.
assert(!Buffer.empty());
ConvertUTF8toUTF32(&Begin8, reinterpret_cast<const UTF8 *>(Buffer.end()),
&Begin32, &C + 1, lenientConversion);
Buffer = Buffer.drop_front(Begin8 - Begin8Const);
return C;
}
static StringRef toUTF8(UTF32 C, MutableArrayRef<UTF8> Storage) {
const UTF32 *Begin32 = &C;
UTF8 *Begin8 = Storage.begin();
// The case-folded output should always be a valid unicode character, so use
// strict mode here.
ConversionResult CR = ConvertUTF32toUTF8(&Begin32, &C + 1, &Begin8,
Storage.end(), strictConversion);
assert(CR == conversionOK && "Case folding produced invalid char?");
(void)CR;
return StringRef(reinterpret_cast<char *>(Storage.begin()),
Begin8 - Storage.begin());
}
static UTF32 foldCharDwarf(UTF32 C) {
// DWARF v5 addition to the unicode folding rules.
// Fold "Latin Small Letter Dotless I" and "Latin Capital Letter I With Dot
// Above" into "i".
if (C == 0x130 || C == 0x131)
return 'i';
return sys::unicode::foldCharSimple(C);
}
static uint32_t caseFoldingDjbHashCharSlow(StringRef &Buffer, uint32_t H) {
UTF32 C = chopOneUTF32(Buffer);
C = foldCharDwarf(C);
std::array<UTF8, UNI_MAX_UTF8_BYTES_PER_CODE_POINT> Storage;
StringRef Folded = toUTF8(C, Storage);
return djbHash(Folded, H);
}
uint32_t llvm::caseFoldingDjbHash(StringRef Buffer, uint32_t H) {
while (!Buffer.empty()) {
unsigned char C = Buffer.front();
if (LLVM_LIKELY(C <= 0x7f)) {
// US-ASCII, encoded as one character in utf-8.
// This is by far the most common case, so handle this specially.
if (C >= 'A' && C <= 'Z')
C = 'a' + (C - 'A'); // fold uppercase into lowercase
H = (H << 5) + H + C;
Buffer = Buffer.drop_front();
continue;
}
H = caseFoldingDjbHashCharSlow(Buffer, H);
}
return H;
}